This invention relates in general to electric heaters and in particular to electric heaters designed to be wall mounted.
Conventionally, electric heaters have been of either the axial fan or blower type. The blower type has utilized a scroll arrangement in combination with the blower wheel to push air in the radial direction of the blower wheel. The fan type heaters have been used in the past to direct air axially through the fan blades. The blower is an air moving device having performance characteristics that depend not only on the blower wheel, but also, and to an important degree, on the scroll shaped housing containing the wheel. The fan is an air moving device with performance characteristics that depend on the impeller alone or the impeller in combination with the cylindrical shaped housing.
Blower designs utilize an elongated wheel having blades arranged generally parallel to the axis of the wheel. The blower, in combination with the scroll, operates such that the scroll guides air into the heel of the blower with as little turbulance, friction and air loss as possible. Further, the scroll collects air from the wheel periphery and with a minimum of recirculation directs it to a single outlet. By using a scroll design of the archimedic and logarithmic types, the space between the wheel and the housing progressively increases, thereby converting some of the velocity pressure developed by the wheel into static pressure as the air is pushed radially around the scroll by the blower wheel. The use of the archimedic or logarithmic spiral as a basis for the scroll design is well-known when used in combination with a blower assembly. In the blower design, the spiral is continued from below the horizontal centerline of the wheel around the wheel and well past the intersection of the vertical center line of the wheel. When used in a heating apparatus, the blower must be in relationship to the heating elements so as to cause the air moved by the blower to pass through the elements and be warmed. Devices of this type are generally large and have not been well suited for wall mounting, particularly in residential wall mounting applications where it is desirable for the heater to mount between standard sized building joists or studs.
For fan type heaters, since air is drawn and propelled axially through the blades in a direction generally parallel to the axis of the fan, the heating elements must be arranged in front of the air flow generated by the fan blades for efficient operation. Also, there must be a free flow of air through the fan. In a wall mounted application, the axial fan is at a disadvantage since the rearward end of the fan is generally closed off. Also, the need to arrange the heating elements in front of the air flow has required the use of a large heater apparatus. To slim the axial fan heater, air circulation becomes a problem requiring the air to be moved in a number of different directions thereby creating operating noise. Thus, it has been difficult to utilize a fan type heater in a wall mounted application.
There is a need in the field for an improved heater assembly capable of wall mounting for providing a smooth air flow through the heating elements with little or no back pressure and little or no recirculation. Also there is a need in the field for a heater mountable between standard sized joists or studs in a residential construction. Further, there is a need for a wall mountable heater capable of drawing a sufficient amount of air from the surroundings and of generating a large capacity of heated air into a room. There is also a need in the field for a wall mountable electric heater apparatus which will operate with comparatively little noise.